1. Field of the Invention
The present invention relates to construction engineering and, more particularly, the invention relates to running pipelines laid directly in the ground using a trench or trenchless method.
2. Description of the Prior Art
Well known in the art are pipelines made of separate pipes connected to each other through hermetically sealed joints.
Such a pipeline required a lot of materials since it is made completely of commercial materials.
In addition, it is complex in manufacture because use is made of pipes, which are insulated and connected to each other and then laid into the ground.
Also known in the art is a pipeline comprising an external envelope made by forcing an annular layer of a binder into a hole formed in the ground, in which case the internal surface of this envelope is provided with a sealing layer in the form of an elastic polymer sleeve. (Cf. USSR Inventor's Certificate No. 870607, cl. EO2 F 5/10, published in 1979).
Such a pipeline is designed for a pressure not higher than 0.3 MPa and therefore, it is not used for pumping an agent but is used for meliorative structures. This is due to the fact that mechanical strength is provided only by the layer of the binder.
Also, this pipeline cannot be used as a drain pipe since it is hermetically, sealed, when the tightness is disturbed it decays in a short time because the binder layer is not secured to the ground and any movement of the latter results in destruction of the pipeline.
A large amount of material is necessary for making the pipeline since the load-carrying capacity and mechanical strength are provided by the binder layer only. In this case the binder layer is not densed.
The pipelines are made essentially by forming a trench, into which a pipe is laid, then the trench is filled with ground.
This method is disadvantageous in that it requires a lot of excavation and earth moving. The pipe is made at an industrial plant and transported to the pipeline laying site, and this is associated with a large consumption of material and high transportation cost.
Also presently known is a worldwide practice which is a method of laying a pipeline in the ground by forming a hole in this ground and lining this hole with an elastic material and a binder. Polymer sleeves are mainly used as an elastic material and cement-and-sand mortar is used or adhesive is used as a binder.
The materials are relatively inexpensive and widely spread over the Earth. The pipelines made of these materials have a long life and are not subject to accumulation of deposits. Furthermore, the process of laying the pipelines made of these materials is simple and economically expedient.
However, in spite of many advantages of such pipelines, they have not found wide application in the world as pressure lines for pumping various agents because they feature insufficient mechanical strength and stand pressure not exceeding 0.3 MPa.
The pressureless pipelines require a considerable amount of materials since in this case the ground does not carry a load and the binder layer is not secured to the ground.
Another significant disadvantage is that the known method cannot be used for development of pipelines more than 200 mm in diameter since such a pipeline is subject to destruction due to insufficient transverse and longitudinal strength.
These are also unsuitable for making drain pipelines because it is difficult to control the degree of ground porosity and the thickness of the binder layer since the pressure of the working agent inside the pipeline is not controlled.
The laid pipelines often lose their tightness and quickly get out of order since their tightness is provided only by the binder layer and the sleeve thickness.
Also known in the art is a device for trenchless laying of pipelines by static puncture technique. This device includes a casing tube, a conical tip, pressure equipment and a support wall (cf. USSR Inventor's Certificate No. 876877, IPC EO2 F 5/18, published in 1981).
The casing tube is used for making a puncture in the ground. It is driven into the ground by a piston of a hydraulic pump, and a hydraulic cylinder thrusting against a supporting wall forces the casing tube into the ground.
Since the device includes a casing tube, it cannot be practically used for laying long pipelines.
The reason is that when the casing tube starts entering the ground, the friction forces increase and resist the motion of the tube in the ground.
Therefore, with a definite length of the puncture the force of friction exceeds the force developed by the piston and this prevents further penetration of the tube into the ground.
The length of the puncture provides by this device does not exceed 100 m.
Known in the art is a device for making a pipeline, which comprises an annular working member for trenchless laying of the pipeline. This device is mounted on a basic machine and a cutter and a system of pipelines with nozzles for feeding a mixture, from which the pipe in the ground is made (cf. USSR No. 429239, cl. F16 L 1/10, EO2 F 5/10, published in 1974).
This device is disadvantageous in that after making the pipe, it must get free of the ground, since the pipe made of a mixture is formed in an annular ring made in the ground. The binder layer almost does not carry a load and is used purely for sealing the pipeline wall.
Known in the art is a device for making a pipeline in a ground consisting of a propelling unit whose frame carries a working member for making a hole in the ground and a mechanism transferring the layers of the pipeline into the formed hole, and a pipeline supercharging system mounted stationarily at the place of origination of said pipeline.
The working member for forming a hole in the ground is made of a drainer having an inner space, in which is mounted a mechanism for forming a layer of an envelope of a binding material, said mechanism consisting of a mixture and an extruder forming the envelope layer. The mechanism for putting the envelope layers into the hole comprises a drum mounted on the propelling unit and a drainer pillar rigedly secured to the propelling unit frame. The pillar has an opening for insertion of the layers communicating through the drainer with the hole formed in the ground.
The supercharging system comprises a compressor installed at the beginning of the pipeline and a unit for controlling the pressure in the pipeline consisting of two spring-loaded rollers, through which the envelope layer formed as a sleeve passes (of. USSR Inventor's Certificate No. 870607, cl. EO2 F 5/10, published in 1979).
The envelope is formed as follows.
The working member forms a hole in the ground by moving the drainer through the ground. After the drainer a sealing layer in the form of a polymer sleeve is laid into the hole. Then an envelope made of a binder is formed by the extruder in the annular space between the sleeve and the ground.
The known device has the following disadvantages:
one cannot obtain a pipeline operating under a pressure exceeding 0.3 MPa;
it is difficult to form pipeline whose diameter exceeds 250 mm.
These disadvantages stem from the fact that a pressure that can be developed in the pipeline is limited by its mechanical strength so it is impossible to produce a pressure inside the pipeline that would cause imbedding of the binder into the ground. Even if such a pressure can be produced, it is not possible to force the binder into the ground for a considerable depth because the layer of the binder (mixture) on the pipeline wall is thin (5-20 mm) and is determined by the annular space between the ground and the working member elements.
Furthermore, this device does not allow one to expand the ground and dense it by the internal pressure of the working agent in order to increase the pipeline strength and tightness.
The known device is unsuitable for laying the reinforcing layers of the pipeline being laid.
Laying of the envelope reinforcement layers into the pipeline wall makes it possible to form pipelines of a high mechanical strength.
The device can form the pipelines only by means of the puncture method and this is not always feasible, e.g. in a rocky ground.
The device cannot be used for making pipelines when the hole in made in the form of a trench.